paper

Rapid Variability of Blazar 3C 279 during Flaring States in 2013-2014 with Joint Fermi-LAT, NuSTAR, Swift, and Ground-Based Multi-wavelength Observations

arXiv:1502.04699 · doi:10.1088/0004-637X/807/1/79

Abstract

We report the results of a multi-band observing campaign on the famous blazar 3C 279 conducted during a phase of increased activity from 2013 December to 2014 April, including first observations of it with NuSTAR. The -ray emission of the source measured by Fermi-LAT showed multiple distinct flares reaching the highest flux level measured in this object since the beginning of the Fermi mission, with of photons cm s, and with a flux doubling time scale as short as 2 hours. The -ray spectrum during one of the flares was very hard, with an index of , which is rarely seen in flat spectrum radio quasars. The lack of concurrent optical variability implies a very high Compton dominance parameter . Two 1-day NuSTAR observations with accompanying Swift pointings were separated by 2 weeks, probing different levels of source activity. While the 0.570 keV X-ray spectrum obtained during the first pointing, and fitted jointly with Swift-XRT is well-described by a simple power law, the second joint observation showed an unusual spectral structure: the spectrum softens by at 4 keV. Modeling the broad-band SED during this flare with the standard synchrotron plus inverse Compton model requires: (1) the location of the -ray emitting region is comparable with the broad line region radius, (2) a very hard electron energy distribution index , (3) total jet power significantly exceeding the accretion disk luminosity , and (4) extremely low jet magnetization with . We also find that single-zone models that match the observed -ray and optical spectra cannot satisfactorily explain the production of X-ray emission.

arXiv comment17 pages, 10 figures, accepted for publication in The Astrophysical Journal

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